0.1.9 • Public • Published



    Licensed under the MIT license


    usertiming-compression.js compresses data from UserTiming. A companion script, usertiming-decompression.js, converts the compressed data back to the original form.

    UserTiming is a modern browser performance API that gives developers the ability the mark important events (timestamps) and measure durations (timestamp deltas) in their web apps. The PerformanceTimeline has several methods such as performance.getEntriesByType('mark') or performance.getEntriesByType('measure') that return each mark or measure's startTime (timestamp) and duration (for measures).

    usertiming-compression.js applies several data-compression techniques to reduce the size of your serialized UserTiming data to 10-15% of it's original size in many cases. See this blog post for a description of these techniques.

    usertiming-decompression.js is a companion script that will take the compressed UserTiming data and build it back to its original UserTiming form (eg. performance.getEntriesByType('mark')) for analysis.


    Releases are available for download from GitHub.

    Web - Compression

    Development: (UMD) usertiming-compression.js - 20kb

    Development: (window.UserTimingCompression) usertiming-compression.vanilla.js - 20kb

    Production: (UMD) usertiming-compression.min.js - 4.0kb minified, 1.6kb gzipped

    Production: (window.UserTimingCompression) usertiming-compression.vanilla.min.js - 3.8kb minified, 1.6kb gzipped

    Web - Decompression

    Development: (UMD) usertiming-decompression.js - 16kb

    Development: (window.UserTimingCompression) usertiming-decompression.vanilla.js - 15kb

    Production: (UMD) usertiming-decompression.min.js - 3.7kb minified, 1.5kb gzipped

    Production: (window.UserTimingCompression) usertiming-decompression.vanilla.min.js - 3.5kb minified, 1.5kb gzipped


    usertiming-compression.js is also available as the npm usertiming-compression module. You can install using Node Package Manager (npm):

    npm install usertiming-compression


    usertiming-compression.js is also available via bower. You can install using:

    bower install usertiming-compression


    Compression and decompression can be done on the command line via:

    node cmd.js
    $ node cmd.js --help
      Usage: cmd [options] [command]
        decompress <file>  decompress file
        compress <file>    compress file
        -h, --help           output usage information
        -V, --version        output the version number
        -o, --output <file>  Output file
        -p, --pretty         Pretty JSON
        -v, --verbose        Verbose debugging


    Please see the W3C UserTiming API Reference for details on how to use the UserTiming API.


    To include usertiming-compression.js, include it via a script tag:

    <script type="text/javascript" src="usertiming-compression.vanilla.min.js"></script>

    Once included in the page, a top-level UserTimingCompression object is available on window.

    If AMD or CommonJS environments are detected, you can use the UMD version:

    <script type="text/javascript" src="usertiming-compression.min.js"></script>

    From the NPM module:

    var UserTimingCompression = require("usertiming-compression").UserTimingCompression;

    To get a map of compressed UserTiming names to values, you can call:

    var utMap = UserTimingCompression.getCompressedUserTiming(options);
    // {
    //     "mark1": "2s",
    //     "mark2": "5k",
    //     "mark3": "8c"
    // }

    If you have a map of mark / measure names you want to use, pass them in as

    var utMap = UserTimingCompression.getCompressedUserTiming({
        map: {
            "mark1": 0,
            "mark2": 1,
            "mark3": 2
    // {
    //     "0": "2s",
    //     "1": "5k",
    //     "2": "8c"
    // }

    If you want to further compress this list for a format suitable for URL transmission (e.g. on a query string), you can use compressForUri():

    var utData = UserTimingCompression.compressForUri(utMap);
    // ~(m~(ark~(1~'2s~2~'5k~3~'8c)))



    Gathers all UserTiming marks and measures from the root HTML page and all accessible IFRAMEs.


    • options (optional)
    • A map of names to indexes to use for compression.
    • options.from: The minimum startTime
    • The maximum startTime
    • options.window: window object that will be queried for UserTiming data

    Returns: A map of names to compressed values.

        "mark1": "2s",
        "mark2": "5k",
        "mark3": "8c"


    Takes the output of getCompressedUserTiming() and converts it into a string suitable for URI encoding.


    • map A map of names to string values

    Returns: A map of names to compressed values.


    Note: The first character of the string denotes what type of compression is used:

    1. ~ is optimized Trie (JSURL) compression
    2. 0 is a tilde array
    3. 1 is a mapped array


    To include usertiming-decompression.js, include it via a script tag:

    <script type="text/javascript" src="usertiming-decompression.vanilla.min.js"></script>

    Once included in the page, a top-level UserTimingDecompression object is available on window.

    If AMD or CommonJS environments are detected, you can use the UMD version:

    <script type="text/javascript" src="usertiming-decompression.min.js"></script>

    From the NPM module:

    var UserTimingDecompression = require("usertiming-compression").UserTimingDecompression;

    To decompress your resources, you can call:

    var original = UserTimingDecompression.decompressUserTiming(utData);



    Decompresses data from a URI-encoded form.


    • data Data compressed via compressForUri()

    Returns: The original UserTiming data



    Tests are provided in the test/ directory, and can be run via mocha:

    mocha test/*

    Or via gulp:

    gulp test

    Version History

    • v0.1.0 - 2015-12-10: Initial version
    • v0.1.1 - 2016-04-04: getCompressedUserTiming() gathers Measures that end after the specified from
    • v0.1.2 - 2016-04-04: Protect against X-O frame access that crashes some browsers
    • v0.1.3 - 2016-07-25: getCompressedUserTiming() accepts an alternate window param passed into options
    • v0.1.4 - 2016-08-10: Round duration values on Measures to nearest millisecond
    • v0.1.5 - 2017-10-01: Fixed NPM entry point
    • v0.1.6 - 2018-11-21: Changed build process to produce UMD (for Node/require) and "Vanilla" (for Browser) files in dist/
    • v0.1.7 - 2018-11-21: Ensure dist/ is published in bower
    • v0.1.8 - 2018-11-21: Also include *.vanilla.js in NPM
    • v0.1.9 - 2019-09-17: Fix: Compression on Trie nodes that are prefixes of another


    Parts of JSURL were incorporated into this library. This project builds upon the work of ResourceTiming Compression, with guidance from Philip Tellis and others at SOASTA.




    npm i usertiming-compression

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